import java.util.Scanner;

public class PP35
{
public static void main(String[] args)
{
int x1;
int x2;
int y1;
int y2;
double result;
double root1;
double root2;
double root3;
double root4;

Scanner scan = new Scanner(System.in);

System.out.println("x1 = ");
x1 = scan.nextInt();

System.out.println("y1 = ");
y1 = scan.nextInt();

System.out.println("x2 = ");
x2 = scan.nextInt();

System.out.println("y2 = ");
y2 = scan.nextInt();

root1 = x2-x1;
root2 =y2-y1;
root3 = Math.pow(root1,2);
root4 = Math.pow(root2,2);
result = Math.sqrt(root3 + root4);
System.out.println("result : "+result);
}
}

